As methods for accessing from a controlling device on the Internet to a controlled device in a home, a DDNS (dynamic domain name system) and a mail system are available.
The DDNS is a scheme in which an in-home controlled device registers its own address with a DDNS server and receives a specified domain name and port number from an internet-side controlling device to allow the access of the controlling device.
As a protocol for realizing real-time communication, an XMPP (eXtensible Messaging and Presence Protocol) is available (e.g., refer to “Extensible Messaging and Presence Protocol (XMPP): Core”, RFC3920, The Internet Engineering Task Force (IETF), October 2004). One real-time communication scheme using the XMPP is instant messaging (IM) (e.g., refer to “Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence”, RFC3921, The Internet Engineering Task Force (IETF), October 2004). In the instant messaging (IM), it is checked whether or not an IM client (a friend who can perform IM exchange) is online on the Internet and, when he/she is online, chatting, file exchange, and so on can be performed with the IM client.
Also, as a protocol for calling up data or a service existing on another computer, a SOAP (simple object access protocol) is available (e.g., refer to “SOAP Version 1.2”, W3C Recommendation, World Wide Web Consortium (W3C), June 2003). In communications based on the SOAP, messages in which auxiliary information called envelopes are attached to XML (eXtensible Markup Language) documents are exchanged using a protocol such as an HTTP (hyper text protocol). Both a client using a service and a server providing the service have SOAP generation/interpretation engines to allow an object to be called up between different environments.